Mannitol and glucose movement across the Golgi membrane of lactating-rat mammary gland.
1. Purified Golgi-membrane vesicles of lactating-rat mammary gland were penetrated by glucose. 3-O-methylglucose, mannose, fructose, sorbitol and mannitol, but not by lactose or sucrose. 2. The kinetics of mannitol uptake and release were followed at 2-6 degrees C with the aid of fine filters (0.45 micrometers pore size) to separate the vesicles from the medium. 3. Mannitol efflux exhibited apparent first-order kinetics with k approximately 1 min-1. Neither saturability, nor inhibition by excess sorbitol or glucose, could be observed. 4. Mannitol efflux at 18 degrees C was about seven times faster than at 1 degrees C, and rates at higher temperatures were too fast to be measured. The rate of glucose efflux at 2-6 degrees C exceeded that of mannitol severalfold. 5. These findings imply a channel or carrier of definite, but limited, specificity straddling the Golgi membrane and able to supply glucose for lactose synthesis.
D000818:Animals; D005260:Female; D005374:Filtration; D005947:Glucose / Q000378:metabolism*; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008353:Mannitol / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D013012:Sorbitol / Q000494:pharmacology
D008353:Mannitol; D013012:Sorbitol; D005947:Glucose